[ConstantFold] Remove redundant constantFoldCompareGlobalToNull() fold (NFCI)

This is already handled in evaluateICmpRelation().

Author: nikic

llvm/lib/IR/ConstantFold.cpp

@@ -1252,25 +1252,6 @@ static ICmpInst::Predicate evaluateICmpRelation(Constant *V1, Constant *V2) {
   return ICmpInst::BAD_ICMP_PREDICATE;
 }
 
-static Constant *constantFoldCompareGlobalToNull(CmpInst::Predicate Predicate,
-                                                 Constant *C1, Constant *C2) {
-  const GlobalValue *GV = dyn_cast<GlobalValue>(C2);
-  if (!GV || !C1->isNullValue())
-    return nullptr;
-
-  // Don't try to evaluate aliases.  External weak GV can be null.
-  if (!isa<GlobalAlias>(GV) && !GV->hasExternalWeakLinkage() &&
-      !NullPointerIsDefined(nullptr /* F */,
-                            GV->getType()->getAddressSpace())) {
-    if (Predicate == ICmpInst::ICMP_EQ)
-      return ConstantInt::getFalse(C1->getContext());
-    else if (Predicate == ICmpInst::ICMP_NE)
-      return ConstantInt::getTrue(C1->getContext());
-  }
-
-  return nullptr;
-}
-
 Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate,
                                                Constant *C1, Constant *C2) {
   Type *ResultTy;
@@ -1309,14 +1290,6 @@ Constant *llvm::ConstantFoldCompareInstruction(CmpInst::Predicate Predicate,
     return ConstantInt::get(ResultTy, CmpInst::isUnordered(Predicate));
   }
 
-  // icmp eq/ne(null,GV) -> false/true
-  if (Constant *Folded = constantFoldCompareGlobalToNull(Predicate, C1, C2))
-    return Folded;
-
-  // icmp eq/ne(GV,null) -> false/true
-  if (Constant *Folded = constantFoldCompareGlobalToNull(Predicate, C2, C1))
-    return Folded;
-
   if (C2->isNullValue()) {
     // The caller is expected to commute the operands if the constant expression
     // is C2.